Inspection techniques for semiconductor manufacturing processes include etching techniques such as reactive ion etching, focus ion beam etching, and chemical etching. Etching of semiconductor wafer specimens has traditionally been used for masked film/layer removal. However, etching can also be used for defect analysis and metrology by inspecting the stacks of materials that make up a wafer. In reactive ion etching, the ions react with the surface material of the sample to form an evaporative material that thereby evaporates from the sample. An obstacle encountered with this technique presents itself when dry etching some materials such as copper. When the copper is bombarded with Cl-containing reactive gases, a copper chloride material, CuClx, is formed over the surface of the copper. This chloride material fails to evaporate well at room temperatures. Accordingly, the sample needs to be heated to temperatures that are significantly higher than room temperature to facilitate evaporation of the CuClx, material. For example, the substrate of sample must be heated to above 200° C. in order to etch Cu films. In many cases, a conventional dry etch process prevents the sample from being used in production since the high temperatures tend to damage the sample.
Another obstacle encountered with the etching process involves determining the endpoint for each etching process. An endpoint refers to the point at which an etching process is terminated because a specific metal, oxide, or photo resist has been fully removed.
Consequently, improved techniques and systems for etching materials, such as Cu, to produce fine patterns at low temperature are needed. Additionally, techniques and systems for etching samples which do not destroy the sample are needed. Preferably, a dry etching mechanism that works at room temperatures for materials which cannot be conventionally dry etched at room temperatures is needed. Also, techniques for accurately determining the endpoint of such etching techniques would be desirable.